A similar device in the form of a valve timing control device has been disclosed in Patent Document 1 cited below. As disclosed in Patent Document 1 this device has a drive rotor 2 driven by a crankshaft (not shown) and a guide plate 27 (which corresponds to a first control rotor of the present invention) rotatable relative to the drive rotor 2. The camshaft 1 of the device has a lever member 18 which is integral with the camshaft 1 and rotatably coupled at one end thereof to one end of a pair of link arms (16a and 16b) with a pin 25. The other end of the link arm (16a and 16b) are rotatably connected to the front ends of operative members (14a and 14b) by means of pins 24. The operative members are provided on the front ends thereof with protrusions 26 that engage with spiral guides 32 formed in the rear end of a guide plate 27. The rear ends of the operative members (14a and 14b) are configured to engage guide grooves (11a and 11b) which extend substantially in the radial direction (the grooves hereinafter referred to as radial guide grooves.)
When the guide plate 27 is attracted by an electric magnet 29, the guide plate 27 is retarded in rotation relative to the drive rotor 2. Then, the protrusions 26 of the front ends of the operative members (14a and 14b) are displaced in the spiral guides 32, while the rear ends are displaced along the radial guide grooves (11a and 11b) in the radially inward direction of the drive rotor 2. In this case, the link arms (16a and 16b) are rotated about the pin 25 relative to the lever member 18 in the clockwise direction (as viewed from the guide plate 27). As a consequence, the phase angle of the camshaft 1 relative to the drive rotor 2 (that is, the relative phase angle between the crankshaft and the camshaft) is advanced in the direction R as shown in FIG. 4 (the direction referred to as phase angle advancing direction), thereby varying the valve timing of the valves.